I like Willa, but Capri is.. odd. no offense. I don't say it's ugly, just very unusual.WillaCapri is cool, but someday you'll must provide a very good reason when your daughter ask you why you name her Capri. It's remind me of capricorn, the zodiac with a mountain goat as its symbol.
however, I think the combo itself is cute.

Willa is not a name that is well heard of in the UK but I understand it is fairly usual in the US. If your husband really really loves it and you also love it then I can't see the problem. It's not as if you're saying he likes it but you're not keen. I say go with it. As for Capri - in the UK that's a type of car but again if you love it then you should go with it.
I know what you mean about not committing. We have a boys name picked and although I do love it I'm not sure it's perfect and nothing we come up with is. OH can't come up with a girls name at all so at least you're most of the way there!
Why not sort of agree on WillaCapri but have a back up name and see what she looks like when she arrives?

Hi! Willa is a wonderful name, and it's great you have so much love for this combo.

My one thought is are you likely to try for more children - if you have a boy, would you be interested in naming him William?

If so, then you might want to wait on Willa, or, put it in the middle (I don't have any objection to one middle name and one first name overlapping in a sibset, I know some do, but, in any case it's more doable than Willa and William).

Seriously contemplating Willa ourselves. One minute I love how it's sweet, feminine, strong, and literary, the next minute I worry that it sounds incomplete or a lazy attempt at Willow. My husband's MN is also William, so I am in a VERY similar situation. I hate that I'm the one that suggested it, and yet I'm the one having second thoughts. I love your pairing with Capri. It's perfect!

I had major cold feet two years ago naming my daughter. I knew I wanted to call her Gigi and was looking for the perfect first name that started with G. My favorite was always Ginger. Half of the feedback was positive and half was negative. There were so many other "safer" name choices like Georgia and Genevieve. I am so glad I stuck to my guns because I am still in love with her name. I can't imagine her with any other name. I can see where you might think Willow is a bit safer, but I would say if you just can't shake a name then use it!